Coach Jupp Heynckes has said Bayern Munich must return to winning ways on Wednesday in the German Cup to bounce back from their shock first Bundesliga defeat of the season. \"It is not the right time to fool around,\" Heynckes fumed at a reporter when asked if goalkeeper Manuel Neuer would venture forward as he did at the end of Bayern\'s 2-1 defeat at home to Leverkusen on Sunday. Bayern are home to Kaiserslautern in the second round of the German Cup on Wednesday and need a win to restore confidence. \"(Kaiserslautern) have nothing to lose and we have everything to lose. It will be a difficult game,\" warned Dutch winger Arjen Robben, who played the last 30 minutes of Bayern\'s defeat after returning from a hamstring injury. Kaiserslautern, who are third in Germany\'s second division, drew 3-3 at mid-table Cologne on Friday. Heynckes admitted he was irritated at how quickly the German media have changed their angle of reporting after defeat, despite his team topping the league. \"(Last week) we were unbeatable, because we dominated the league, now everything is discussed and painted with controversy,\" he said. \"We have to deal with it but one thing is clear: my team is established and knows what it can do.\" Heynckes said he has \"no doubts\" last season\'s losing German Cup finalists will see off Kaiserslautern because of the strength in depth in his squad. Reserve team goalkeeper Tom Starke is likely to make his first start of the season for Germany first choice Manuel Neuer, while other squad members Rafinha, Anatoliy Tymoshchuk and reserve striker Claudio Pizarro are set to feature. But whoever plays, Heynckes has warned his team have \"an obligation\" to put in a motivated performance with a crowd of 71,000 expected. There are also a few nervous glances at last year\'s results now. In October 2011, Bayern lost at Hanover, ending an eight-match unbeaten run in the league, then lost to Dortmund and Mainz which allowed the pursuing pack to catch up with them. \"We need to learn from last year,\" said Robben. \"(Defeat to Leverkusen) was a wake-up call. We have to react immediately. Obviously, we can\'t start dropping lots of points and allow our rivals to come back at us.\"